The principle aim of continued study is to extend our fundamental knowledge of carbocations, one of the most significant type of reactive organic intermediates and investigate representative in vitro cyclization, alkylation, and rearrangement reactions of biologically significant systems in which these ions play a significant role. New highly efficient non-oxidizing superacid systems based on boron tris- triflate and its conjugate acids will be developed for improved study of stable carbocations. Preliminary results indicate feasibility of these systems and significant advantages over previously used ones. Study of carbocations will be extended to new systems, including cage hydrocarbons. Methods to be applied to the investigation of carbocation intermediates will include NMR studies, including 13C-13C NMR spin coupling constants, solid state cross polarization-magic angle 13C NMR studies (to establish NMR parameters of the ions in the solid state and compare them with solution data of the same ions). X-ray structure determination of a series of isolate crystalling carbocation salts and their X-ray electron spectroscopic (ESCA) studies will be also carried out. With the proposed work detailed structural studies will be possible on the same ionic intermediates both in solution and in the solid state. As carbocations are the key intermediates both in varied alkylations, cyclizations, rearrangements, their knowledge is essential to a better understanding of these reactions, which can serve as models for enzymatic reactions. Solution studies alone are difficult, however, to relate to behavior at enzymatic sites. Solid state studies will allow a better understanding of relevant intermediates. Specific systems to be studied in regard to their potential bioalkylating ability will be aromatic hydrocarbons known for their carcinogenic activity. Study of derived arenium ion intermediates and related cations (dications) will be carried out under stable ion conditions. Further studies will center on rearrangement-cyclization reactions of biologically significant terpenes and on the interconversion of steroids under stable ion conditions. Studies will also be carried out on acylation, formylation and carboxylation systems emphasizing investigation of such fundamental ions as the formyl and isoformyl cations, carbonic acid, its remarkably stable protonated form and their reactions.